1. Field of the Invention
The present invention relates to an image display device which displays images on a display and a LUT adjustment method for adjusting LUT correction data provided for an image display device.
2. Description of the Related Art
In image display devices such as television receivers, for example, there have conventionally been those in which liquid crystal panels are used as displays, and images are displayed on the liquid crystal panels. Such an image display device is provided with LUTs, which are tables of correction data for correcting the chromaticity of the displayed images, and is designed such that the images are displayed on the liquid crystal panel after correcting the chromaticity based on the LUT correction data. A LUT is a table of correction data for correcting the input values of image data, which indicates the relationship between LUT input values which are the uncorrected values and LUT output values which are the corrected values of the LUT input values. To wit, in such an image display device, the input values of image data are corrected based on the LUT correction data, and images are displayed on the liquid crystal panel based on the corrected input values.
Furthermore, in such an image display device, chromaticity characteristics of displayed images are adjusted to the desired chromaticity characteristics of various types such as the normal type, cool type, and warm type by providing a gain adjusting unit that applies a gain to the input values of image data and adjusting the gain value of the gain adjusting unit (the value of the gain to be applied to the input values of image data).
The LUT correction data is calculated and created using one standard panel as the liquid crystal panel based on the chromaticity of the images displayed on the standard panel. Moreover, the gain values of the gain adjusting unit are also determined using a standard panel based on the chromaticity of the images displayed on the standard panel.
Image display devices have been known (for example, see Japanese Patent Publication No. 3697997) in which the contrast is measured, a dynamic range that can be utilized for display is set, and gain adjustment and offset adjustment are performed to match the dynamic range, and thereafter, the data of the lookup table is recalculated such that the dynamic range becomes the full range, and the recalculated data is written. In addition, display control devices have been known (for example, see Japanese Patent Publication No. 4536582) in which the grayscale values of output image data are used as arguments, logical values indicating whether to use or not are used as array elements in a lookup table of grayscale values represented by the arguments, and the lookup table is generated based on the sum of the arguments and the array elements. Furthermore, video signal processing devices have been known (for example, see Japanese Patent Application Laid-Open Publication No. 2004-180090) in which three primary-color input video signals are subjected to level adjustment at the same gain as each other in accordance with a first gain data set, three primary-color internal video signals are generated, a second gain data set is generated in accordance with the maximum value selected for each pixel unit from the three primary-color internal video signals by using a lookup table that has nonlinear characteristics written thereto with the maximum value selected for each pixel unit from the three primary-color internal video signals as an address, and the lookup table is rewritten in accordance with the input nonlinear characteristic data.
Incidentally, within image display devices, there are differences among individual liquid crystal panels. For the reason, even if one should adopt in an image display device the same LUT prepared based on a standard panel and set the same gain value as the one determined based on the standard panel, the chromaticity characteristics of the images displayed on the liquid crystal panel of the image display device would have characteristics different from the standard chromaticity characteristics (the chromaticity characteristics designed with the standard panel).
Accordingly, in an image display device, in order to set the chromaticity characteristics of a displayed image to the standard chromaticity characteristics, it is necessary to perform white balance and γ adjustments which adjust the chromaticity characteristics of a displayed image. The white balance and γ adjustments could conceivably be done by calculating the LUT correction data (again, calculated anew) and rewriting the data.
However, in cases where the chromaticity characteristics are adjusted by adjusting the gain value of the gain adjusting unit (adjusted to the desired chromaticity characteristics of various types such as the normal type, cool type, and warm type), there is a risk that the expected white balance and γ adjustments cannot be realized because of the gain value being adjusted. That is, there is a risk that white balance and γ adjustments that are appropriate to match the various chromaticity characteristics cannot be realized. Moreover, if the LUT correction data were to be calculated simply to reach the standard chromaticity characteristics, then there is a risk that the maximum brightness of the display would be limited by the maximum output value of the LUT. As a result, there is a risk that one may not be able to take effective advantage of the maximum brightness potential of the display, so the brightness may drop, and there is a risk that appropriate chromaticity corrections cannot be done with respect to high-grayscale images. Note that the aforementioned problems cannot be solved even with the application of the contents disclosed in the aforementioned Japanese Patent Publication No. 3697997, Japanese Patent Publication No. 4536582 and Japanese Patent Application Laid-Open Publication No. 2004-180090.